Logical fallacies

What are logical fallacies ?

Logical fallacies are essentially errors of reasoning in making an argument. When logically fallacious arguments are used, usually based on bad reasoning to support a position (or to try to convince someone to adopt the same position), it is considered a fallacy.

This means that an argument that uses a logical fallacy shouldn’t hold up to those using logic and reason as the source of decision making. Of course, it generally doesn’t stop people, specifically those pushing pseudoscience or an anti-science point of view, from using them or being swayed by them.

There are two forms of a logical fallacy:

Formal–These logical fallacies are those fallacies that violate a particular rule of logic. They almost always include non sequitur logic, that is, the conclusion is not connected to the argument.

Informal– arguments that, while not violating logic rules, are invalid because of the content of their argument. Informal fallacies are often characterised by the fact that there is a disconnect of some kind between their premises and conclusions.

Deciding between formal and informal logical fallacies is interesting for logic geeks, but I didn’t want to spend time separating between the two. The net effect of either type of logical fallacy is the same–the arguments can be dismissed.

List of logical fallacies

Below is a list of the most common fallacies that are used by those who push pseudoscience or deny science – it’s not all inclusive, so I’m missing a bunch:

Not all of this list are technically logical fallacies. For example, confirmation bias is really a cognitive bias, not a logical fallacy. However, for reference purposes, I include it because it forms the basis of logical fallacies like “cherry picking.”

For example, confirmation bias, the gambler’s fallacy, and bandwagon fallacies are fallatious not because the violate logic, but because they represent ways in which our natural view of the world may lead us to fallacious conclusions.

Editor’s note: This page was originally published in March 2015. It has been updated to fix some SEO issues, clarify some biases that are not logical fallacies per se, and clean up some spelling issues.